Drive arrangement for a hybird vehicle

ABSTRACT

A drive arrangement for a hybrid vehicle with an electric motor, which has a rotor with a hub body and a stator, and with two engagable and disengagable dry-disk clutches. Each of the dry-disk clutches has a first functional component as well as a second functional component. The second functional component is frictionally connectable to the first functional component in order to provide a torque transmitting connection.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a drive arrangement for a hybrid vehicle and,more particularly, to a drive arrangement with an electric motor havingan external rotor encased in a hub body, a stator, two dry-disc clutcheslocated across from each other on different axial faces of the hub body,each clutch having first and second functional components, the firstfunctional components being non-rotatably connected to either the crankshaft or the gear shaft of an internal combustion engine, the secondfunctional components being non-rotatably connected to the rotor, andthe first and second functional components frictionally engaging eachother and the dry-disc clutches in a torque transmitting connection.

2. Description of the Prior Art

A hybrid drive for a motor vehicle is known in the art and described inGerman Patent Application No. DE 37 37 192 A1. This motor has internalcombustion engine and an electric motor designed as an asynchronousmachine. The rotor of the electric motor can be connected to the crankshaft of the internal combustion engine via a first dry-disc separationclutch and to the input shaft of the gear via a second separationdry-disc clutch. The internal combustion engine has no flywheel of itsown. Instead, the rotor of the electric motor can be used as theflywheel mass for the internal combustion engine when the first clutchis closed. The rotor of the electric motor, which is located inside ofthe stator, has a hub body that is arranged on the side facing the gearand mounted on the gear input shaft. It is very massive in design andthus constitutes a large part of the flywheel mass. The hub body formsthe support for the clutch disc of the second separation clutch, whichestablishes the frictional connection between the rotor and the gearinput shaft. The first separation clutch is located on the face of theelectric motor facing the internal combustion engine. The clutch disc ofthis first separation clutch is non-rotatably connected fashion to thecrank shaft. In order to establish a frictional connection in theengaged state the first separation clutch has an annular shaped support,also of massive design, which is connected rigidly to the rotor. The twoseparation clutches are thus arranged next to one another on the sameside of the hub body, The output of the electric motor, which functionsas a generator when the hybrid vehicle is operated by the internalcombustion engine alone, i.e. both separation clutches closed and feedsthe vehicle battery and other electric consumers, is equal to only arelatively small fraction of the output of the internal combustionengine and totals, for example, 7 kW. For this reason, the driving powerduring purely electric operation (first separation clutch opened betweenrotor and crank shaft; second separation clutch closed) iscorrespondingly modest. The electric motor in this hybrid vehicle isalso meant to be able to act as a starter for the internal combustionengine. Due to the low output and the relatively low torque that can beproduced, however, direct start-up from a stoppage of the electric motoris not always possible. Therefor, the electric motor is initiallybrought to a relatively high rotational speed with the separationclutches open, so as to store a considerable quantity of energy in therotating flywheel mass of the rotor. Only then is the first separationclutch between the rotor and the crankshaft engaged, jerkily, so thatthe internal combustion engine is revved up to above its starting speedand can then continue to run automatically. Along with these relativelypoor conditions for starting the internal combustion engine, this driveunit has a relatively large axial structural length, which can be anobstacle to installation in standard engine/transmission units.

The object of the invention is therefore to further develop a genericdrive arrangement in such a way that the output capacity of the electricmotor is increased and the start-up of the internal combustion engine isimproved. In doing this, a primary goal is to keep the axial structurallength as small as possible.

SUMMARY OF THE INVENTION

Starting from the known drive arrangement, the invention calls for anelectric motor designed having an external rotor and preferably having apermanent magneto-electric rotor and electronically commutated powersupply of the stator windings. This ensures significantly higher torquesas well as better efficiency. Furthermore, two dry-disc clutches, whichare advantageously equipped with automatic actuation (e.g., hydraulic,pneumatic or electromechanical), are located opposite one another ondifferent sides of the hub part if the rotor. Thus, the hub part liesbetween the two clutches and, in an especially preferred embodiment ofthe invention, directly provides for both clutches a support function(second functional component) for both clutch discs (first functionalcomponent), which are non-rotatably connected to the crank shaft of theinternal combustion engine and/or to the gear input shaft of the drivearrangement. The second functional component of both of the dry-discclutches is thereby advantageously designed as a single piece with thehub part, especially as a thin-walled body that is essentiallycylindrically shaped and is produced, for example, as a comparativelythin-walled sheet metal part or cast part. In this solution, the supportof the two clutch discs is formed from the same structural part in anespecially space-saving manner. It is merely necessary that the wallthickness of the hub part in this area be such that the frictionalenergy associated with the maximum torque of the internal combustionengine or the electric motor (if higher) can be absorbed and divertedduring the coupling process. The flywheel mass of this electric motorcan be relatively much lower, because it can produce significantlyhigher torque and an accordingly higher output, even making it possible,as a rule, to start the internal combustion engine from a stoppedelectric motor without first bringing the electric motor to a high speedin order to store energy.

The hub part of the rotor can be mounted either on the crank shaft or onthe gear input shaft. Mounting on the crank shaft is preferred. Ineither case, the rotor bearing lies between the two dry-disc clutches.It is advisable to provide at least one of the dry-disc clutches withelements (which are known themselves) to dampen the torsionalvibrations, in order to improve driving comfort during operation withthe internal combustion engine. It is also possible to dampen torsionalvibrations by suitably varying the actual electric load, which iscontrolled by a superordinated electronic controller, in the sense of anoffset of the torsional vibrations.

The design of an electric motor having an external-rotor motor and apermanent magneto-electric rotor allows the rotor to be executed as aannular-shaped body of especially slight thickness (difference betweeninner and outer diameter), so that while the total diameter of the motorremains the same, the air gap between the rotor and the stator clearlymoves further to the outside, permitting higher torques to be produced.At the same time, the mass of the magnetic ring acts upon a largediameter, so that considerable flywheel moment is achieved withrelatively small mass, ensuring good concentricity of the internalcombustion engine. In addition, the principle of the external rotor alsopermits the design of the electric motor to have a relatively short inthe axial dimension. The drive arrangement is especially compact whenthe core assembly of the stator windings has a large and substantiallycylindrical recess around the longitudinal axis of the electric motor(up to the vicinity of the windings) and the hub part of the rotor has acentral outward bulge in such a form that at least one of the twodry-disc clutches lies inside of the structural space encompassed by thestarer.

Instead of mounting the rotor directly on the crank shaft or the gearinput shaft, a less preferred indirect mounting may be carried out. Forexample, this can be accomplished as follows: the clutch disc of one ofthe two dry-disc clutches, preferably the dry-disc clutch facing theinternal combustion engine, is fixed and non-rotatably connected to thehub body of the rotor, and the rotor bearing is located in theconnection region. The rotor bearing rests on the structural componentforming the support of this clutch and is fixedly connected to thecrankshaft via the clutch housing. In the case of indirect mounting onthe gear input shaft, the clutch housing of the second dry-disc clutchwould correspondingly be fixedly connected to the gear input shaft.

Another alternative is to mount the rotor on the starer. This can bedone in such a way that the clutch disc of the first dry-disc clutch isin turn connected to the hub body of the rotor and the rotor bearing islocated in the connection region. The rotor bearing rests on anessentially cylindrical carrying part, which is attached to the starerand extends from the outside into the intermediate space between theclutch disc of the first dry-disc clutch and the hub body. Finally, in alittle preferred manner, it is also possible to mount the rotor via thecasing of the internal combustion engine or the casing of the gear.

BRIEF DESCRIPTION OF THE DRAWING

The invention is described below in greater detail with reference to theexamples of the drive arrangements in accordance with the invention andis shown schematically in FIGS. 1 to 3. In the drawings in which likenumbers are used to denote similar elements.

FIG. 1 is a cross-sectional view of the drive unit in accordance withthe present invention with the second functional components of theclutches integrated into the hub body as a single element;

FIG. 2 is a cross-sectional view of the drive unit in accordance withthe present invention with the hub body mounted indirectly on the crankshaft;

FIG. 3 is a cross-sectional view of the drive unit in accordance withthe present invention with the hub body mounted on the stator.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

The drive arrangement shown in FIG. 1 consists of an electric motor thatcan be operated both as an electric motor and as a generator. The drivearrangement further consists of two dry-disc clutches K1 and K2 and islocated inside of a gear bell 24. The electric motor is designed as apermanent magneto-electric d.c. motor with electronic commutation andhas an external rotor 1 which is equipped with a plurality of permanentmagnets 5 of alternating polarity and high field strength (preferablymade of an FeNdB or an SmCo alloy). In order to furnish the electroniccontroller (not shown) in a timely manner with the information about therelative angular position between the stator magnetic poles and thepermanent magnetic poles needed for commutation, a resolver system 26 isprovided. The stator 3, the windings of which are identified byreference number 4, has a core assembly 14, having an axially continuouscylindrical recess around the longitudinal axis of the electric motorthat reaches to near the windings 4. The stator 3 is connected, in amanner not described in greater detail, to the casing of the internalcombustion engine, which is also not . The only part shown of theinternal combustion engine shown in the Figures is the final or endpiece of the crank shaft 13. On its right face, the rotor 1 has acylindrical hub body 2, which is rotatably mounted via rotor bearings 17on the crank shaft 13 between the two dry-disc clutches K1, K2.Alternatively, of course, the stator 3 could also be attached to thegear bell 24. In this case, the hub body 2 would be moved to the leftface of the rotor 1 and the resolver 26 would advantageously be attachedto the gear bell 24. The clutch disc 6 of the first dry-disc clutch K1is non-rotatably connected to the crank shaft 13. The clutch disc 6 isequipped on both sides with friction linings 21. In the engaged positiona diaphragm spring 9 presses the friction linings 21 via a pressureplate 20 against the hub body 2 functioning as a support 7-i.e. the hubbody 2 having a corresponding friction surface-of the rotor 1. Thefrictional connection resulting from this can be released by moving adisconnecting element 19 to the left, which causes a plate-likedisconnecting device 8 to counteract the pressure force of the diaphragmspring 9 via the disconnection bearing 16. In the engaged position aconstant frictional connection is established between the crank shaft 13and the rotor 1 via the dry-disc clutch K1. Because the hub body 2 isprovided with a protuberance pointing to the left, which extends intothe cylindrical recess of the stator core assembly 14, the clutch K1 canbe completely integrated into the structural area encompassed by thestator 3. On the opposite axial face of the hub body 2, the seconddry-disc clutch K2 is located. As its first functional component, thisclutch K2 has a clutch disc 10, which is provided on bath sides withfriction linings 23 and is non-rotatably connected to the gear inputshaft 15. The second functional component 11 of the clutch K2, whichforms the support for the friction linings 23 of the clutch disc 10, isagain intergral with the hub body 2. In the engaged clutch position, thefriction linings 23 are continually pressed against the hub body 2 bymeans of the diaphragm spring 12 via the pressure plate 22 and establisha frictional connection between the rotor I and the gear input shaft 15.By moving the disconnection bearing 18 to the left (activation elementsare not shown in greater detail), it is possible to release thisfrictional connection.

In order to dampen the torsional vibrations, it is possible to provide,in a known manner, torsional damping elements (not shown), whichadvantageously are integrated into the clutch disc 10 of the seconddry-disc clutch K2. In addition or alternatively, the clutch disc 6 ofthe first clutch K1 can also be provided with such torsional dampingelements.

With respect to the electric motor, the embodiment in FIG. 2 is largelythe same as that shown in FIG. 1, so similar elements will not bediscussed again here. The design and arrangement of the dry-disc clutchK2 also corresponds to FIG. 1, while the clutch K1 differs. The firstfunctional component 30 of clutch K1 is formed by a clutch casing 30afixedly connected to the crank shaft 13 and to a support 30b, which isfixedly connected to the clutch casing 30a and has a generallycylindrical shape. The clutch disc 31 is fixedly connected via a hollowcylindrical connecting piece 32 to the hub body 2 of the rotor 1. Theroller bearing 17 for mounting the rotor 1 sits externally on theconnecting piece 32. In the outward direction, the rotor bearing 17rests on the end of the support 30b, which has been shaped into abearing seat and extends from the outside into the intermediate areaformed between the clutch disc 31 and the hub body 2.

In the engaged position, the diaphragm spring 9 presses the clutch disc31 and the friction linings 21 against the support 30b via the pressureplate 20 thereby establishing a frictional connection, transmittingtorque from the crank shaft 13 to the hub body 2 via the clutch casing30a, the clutch disc 31 and the connecting piece 32. Clutch K1 isdisconnected by moving the disconnecting element 10 to the left.

The structure of the drive arrangement in FIG. 3 is essentially the sameas to that in FIG. 2. As in FIG. 2, it is not the clutch disc (as inFIG. 1), but rather the clutch casing 40a that is non-rotatablyconnected to the crank shaft 13 as a part of the first functionalcomponent 40 of the clutch K1. The clutch casing 40a continues in thesupport 40b of the clutch K1. As in FIG. 2, the clutch disc 41 is againfixedly connected to the hub body 2 of the rotor 2 via a hollowcylindrical connecting piece 42, and the rotor bearing 17 rests on thisconnecting piece 42. In the outward direction, the rotor bearing 17 issupported via a generally cylindrically carrying part 43, which isconnected to the stator 3. The frictional connection is established andreleased in the same manner as in FIG. 2. The sole difference in thisembodiment of the invention; as compared to FIG. 2, is the type of rotormounting.

Embodiments of the drive arrangement according to the invention are alsopossible in which, in contrast to FIG. 1, it is not the clutch K1 butrather the clutch K2 that has been modified, in the same manner asclutch K1 in FIGS. 2 and 3, i.e., the assignments of the two functionalcomponents of the clutch K2 to the hub body 2 of the rotor 1 and to thegear input shaft 19 are reversed. In general, it should be noted thatthe clutches K1 and K2 can be actuated in any manner desired. Theclutches may be "pressed" or "pulled"; their engagement anddisengagement may be purely mechanical, as in FIGS. 1-3, or may usepressure-operated piston/cylinder units or even an electric motor orelectro-magnetic drive.

In the particularly preferred embodiment shown in FIG. 1, the drivearrangement according to the invention is able to provide electric drivepower at high torque. This drive arrangement also has a very low weightrelative to its output. It permits the internal combustion engine to bestarted without prior revving up, i.e. without temporary decoupling ofthe rotor from the crank shaft. The higher power capacity of theelectric motor makes it possible to produce a correspondingly higherbraking moment and a more effective resupply of energy into the vehiclebattery during coasting operation of the hybrid vehicle. The higherefficiency of the preferred permanent magneto-electric motor, ascompared to asynchronous motors, also constitutes an importantadvantage. The driving power of the hybrid vehicle in a purely electricoperation are substantially better than those of the vehicle describedinitially.

We claim:
 1. A drive arrangement for a hybrid vehicle comprising: anelectric motor includingan external rotor having a cylindrically shapedhub body and a plurality of permanent magnets; a rotor bearing; and astator; an internal combustion engine including a casing and a crankshaft; a drive train including a casing and a gear input shaft; andfirst and second actuatable clutches positioned on opposing axial facesof said hub body, each clutch having first and second functionalcomponents, said first functional component of said first clutch beingnon-rotatably connected to said crank shaft, said first functionalcomponent of said second clutch being non-rotatably connected to saidgear input shaft, said second functional component of both said firstand second clutches being non-rotatably connected to said hub body ofsaid external rotor, and wherein said rotor bearing is disposed in aposition selected from the group consisting of (a) between said firstand second clutches (b) on said casing of said internal combustionengine and (c) on said casing of said drive train.
 2. The drivearrangement of claim 1, wherein said rotor is mounted to one of saidcrank shaft and said gear input shaft.
 3. The drive arrangement of claim1, wherein said first clutch includes a cylindrically shaped carryingelement fixedly connected to said stator and extending into an annulararea formed by said second functional component of said first clutch andsaid hub body, and a cylindrical connecting piece connected to said hubbody, said rotor bearing being positioned between said carrying elementand said cylindrical connecting piece.
 4. The drive arrangement of claim1, wherein said first functional component includes a clutch casingconnectable to said crank shaft and a cylindrically shaped supportconnected to said clutch casing, wherein said first clutch includes acylindrical connecting piece connected to said hub body, and whereinsaid rotor bearing is positioned between said hub body and saidcylindrical connecting piece.
 5. The drive arrangement of claim 2,wherein said hub body, said second functional component of said firstclutch and said second functional component of said second clutch areintegrally formed.
 6. The drive arrangement of claim 1, wherein said hubbody is cylindrically shaped and includes sheet-like walls.
 7. The drivearrangement of claim 6, wherein said hub body is formed of sheet metal.8. The drive arrangement of claim 1, wherein said stator occupies astructural volume defined within said arrangement and includes electricwindings and a core assembly defining a continuous central cylindricalrecess extending to a point adjacent said windings, said hub bodydefining a central outward bulge whereby at least one of said first andsecond clutches is positioned within said structural volume encompassedby said stator.
 9. The drive arrangement of claim 1, wherein said statorwindings are powered through electronic commutation of said rotor. 10.The drive arrangement of claim 1, wherein at least one of said first andsecond clutches includes torsional vibration damping elements.
 11. Thedrive arrangement of claim 1, further comprising means for actuatingsaid first clutch, said first clutch facing said internal combustionengine, said actuating means extending through said gear shaft.
 12. Thedrive arrangement of claim 11, wherein said actuating means comprises ahollow shaft.
 13. The drive arrangement of claim 1, further comprising ameans for actuating said first clutch, said first clutch facing saidinternal combustion engine, said actuating means comprising apressurized piston/cylinder unit actuated by a pressure medium.